A. FIELD OF THE INVENTION
This invention relates to incinerators and, especially to stationary, vertical incinerators having a number of heat-regenerative sections topped by a common combustion chamber.
B. PRIOR ART
Stationary incinerators using the heat-regenerative principle are known in the art. U.S. Pat. No. 3,895,918 to James H. Mueller, issued July 22, 1975 teaches and claims incineration apparatus in which there is a central, high-temperature combustion chamber with three or more heat-exchange sections arranged around it which communicate with the chamber. Each heat-exchange section includes a large number of saddle-shaped, for example, ceramic elements confined between two substantially vertical apertured retaining walls which were often, in the past, made of apertured metal. Inlet and outlet valves associated with each section were so arranged and operated that when the effluent entered one section substantialy horizontally through its heat-exchange bed, the exhaust valve thereof was closed. At least one other heat-exchange section had its inlet valve closed and its outlet valve, connected to an exhaust fan, open.
While such structures have proved eminently satisfactory and have been commercially successful, certain of its design features imposed rigorous demands on its materials and structural characteristics. For example, in certain ones of those incinerators, the apertured metallic retaining wall for the heat-exchange elements which faced the high-temperature central combustion chamber had to have very high resistance to heat and extreme strength to offset the lateral pressure exerted by the thousands of ceramic elements within the bed partially confined by it. It was often necessary to employ special steels in sufficiently thick gauges which could resist heat, as well as tie-rods, holding pins, springs and leg supports to insure its geometric integrity under such extreme heat and pressure conditions.
The input and exhaust ducts which communicated individually with each of the heat-exchange sections in that prior construction were attached to the sides of the sections at relatively large heights. This made them somewhat more difficult to maintain than if they had been closer to the ground. To compensate for the subsidence over time of the ceramic elements in each bed due to gas velocity, expansion and contraction, etc., these former types of incinerators often required the use of a special fill hatch for charging the bed with additional ceramic elements. These features of some of the prior art structures rendered them quite costly to build and maintain.
As an alternative to the central combustion chamber with flow through it from heat-exchange sections located outwardly thereof, vertical incinerators came into use. Within a cylindrical shell, for example, there were three or more heat-exchange sections having respective generally pie shaped cross-sections into which the heat-exchange elements were placed. Above all the separate heat-exchange sections, each with their own inlet and outlet valves, there was a common combustion chamber. Effluent gases were fed into the bottom of a first of the adjacent heat-exchange sections at relatively low velocity, e.g., 750 ft/min. The gases passed upwardly through the first heat-exchange bed and into the common combustion chamber. Since at least one other of the heat-exchange sections had its inlet valve closed and its outlet valve (coupled to a suction fan) open, no effluent could enter that bed, but the high-temperature products of combustion from the combustion chamber would be pulled downward through it to exhaust. One of the problems encountered with such types of vertical incinerators was the fact that, since the effluent gas entered the combustion chamber at relatively low velocity, it would seek the shortest path within the chamber, i.e., to the adjacent bed operating in the exhaust mode, to exhaust. Therefore, the effluent did not remain in the combustion chamber for sufficient time to permit its substantially complete combustion at the high temperatures involved. Consequently, gases exhausted through the second bed were not raised to the proper temperature to sufficiently purify them and so when they passed through the ceramic elements in the second bed, those elements were insufficiently heated to preheat the effluent when applied to that bed during its next cycle of operation as an inlet heat-exchange section.
It is therefore among the objects of the present invention to provide:
1. A stationary, vertical-flow incinerator of the heat-regenerative type in which the effluent gas being processed is made to reside within the common combustion chamber for a time sufficient to purify it by incineration.
2. Incineration apparatus in which relatively low velocity effluent gas input flow is converted to relatively high velocity as it enters the combustion chamber so as to produce more gaseous turbulence in that chamber thereby helping to insure attainment of the proper residence time for the effluent in that chamber as well as production of more even heat distribution therein.
3. A stationary, vertical flow incinerator of the heat-regenerative type of simplified and relatively less expensive construction.